Children with specific language impairment (SLI) often show an especially serious limitation in the use of grammatical morphology. These difficulties include problems with bound morphemes such as past tense and third person singular inflections, an functions words such a articles and auxiliary verbs. The purpose of this project is to explore the possible bases of these grammatical morpheme limitations, and to examine how such limitations might hinder other aspects of these children's language development. To accomplish this general goal, the grammatical morpheme comprehension and production abilities of children with SLI will be examined across three languages: English, Cantonese, and Spanish. Data from these different languages will be used to assess the relative adequacy of five recent accounts of grammatical difficulties in English-speaking children with SLI. Because the morphological properties of Cantonese and Spanish differ from those of English in critical ways, they offer a clearer view of the contribution of factors that are confounded in English, thereby facilitating interpretation of the data obtained from the English-speaking children with SLI. Inclusion of these other languages will also permit a stronger test of whether problems in word order are related to deficits in grammatical morphology, and whether problems with grammatical aspect contribute to the children's difficulty with tense. An understanding of the source of these children's problems with grammatical morphology and the role these problems play in other areas of language should lead to more appropriate treatment procedures for these children.